Location services for mobile communication system

ABSTRACT

There is disclosed a method of providing location information in a mobile communication system, comprising the steps of: receiving a request for a current location of a mobile station; determining a time at which a last known location of the mobile station was determined; comparing the time to a threshold time limit; and providing, as the current location, the last known location if the time is within the threshold time limit.

FIELD OF THE INVENTION

The present invention relates to the provision of location informationin mobile communication networks, and particularly in applications wherea request is made for a current location of a mobile device. Theinvention is particularly but not exclusively concerned with locationbased services in second and third generation mobile communicationsystems.

BACKGROUND OF THE INVENTION

In mobile communication systems, network operators are always concernedabout radio resource usage. There is a general aim to optimise radioresource usage.

The provision of location services in mobile communication services,which is likely to be a key service aspect of future mobilecommunication systems, adds an additional burden to radio resources,since with current techniques there is a need for additional radiosignals to provide information relating to a current location of amobile station. In particular, in current proposals for locationservices there is a requirement for mobile stations which are in idlemode to be paged in order to obtain there location responsive to apaging request.

In customised applications for mobile network enhanced logic (CAMEL)phase 1 and phase 2, if a mobile station is active then the activesession is used to identify a current cell global identity (CGI) orservice area identity (SAI) for the mobile station. Additionally inCAMEL phase 2 if the mobile station is idle, then the last knownlocation for the mobile station is returned. However, the last knownlocation for the mobile station in idle mode may no longer provideuseful information if the mobile station has moved significantly sinceits last known location was recorded.

In CAMEL phase 3, if a mobile station is active then the active sessionis again used to identify a current location of the mobile station,either the cell global identity (CGI) of GSM radio access network orservice area identity (SAI) of UMTS radio access network. If the mobilestation is idle, however, then the idle mobile station may be paged inorder to obtain updated location information. The mobile station ispaged if the current location is requested. This provides more usefullocation information in idle mode, but increases the radio resourceusage.

In third generation based location services, as with CAMEL phase 3, if amobile station is idle it is always paged and a location request issuedto it again increasing the radio resource usage. Standard LCSfunctionality differs from CAMEL phase 3 in that paging is always donefor an idle mode mobile station.

It is an aim of embodiments of the present invention to facilitatelocation services whilst minimising any usage of radio resources, andthereby minimise one or all of the problems mentioned above.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method ofproviding location information in a mobile communication system,comprising the steps of: receiving a request for a current location of amobile station; determining a time at which a last known location of themobile station was determined; comparing the time to a threshold timelimit; and providing, as the current location, the last known locationif the time is within the threshold time limit.

The method may further comprise the steps of: determining a currentlocation of the mobile station if the time is not within the thresholdlimit; and providing, as the current location, the obtained currentlocation.

The step of comparing the time to the threshold time limit may bedependent upon the status of the mobile station. If the mobile stationis active the comparing step may be disabled and a current location isdetermined for the mobile station. If the status of the mobile stationis idle, the comparing step may be enabled.

If a current location is not provided, the last known location may beprovided as the current location.

The method according may further comprise the step of storing the lastknown location of a mobile station together with a time associated withthe last known location. The method may further comprise the step ofstoring the threshold time limit. The method may further comprise thestep of dynamically adjusting the threshold time limit.

The threshold time limit may be set by a network operator. The thresholdlimit may be included in the request for the current location. The timemay be an elapsed time.

According to the present invention there is further provided a method ofproviding location information in a mobile communication system,comprising the steps of: receiving at a network element a request froman application for a current location of a mobile station; determining,at the network element, a time at which a last known location of themobile station was determined; comparing, at the network element, thetime to a threshold time limit; and providing to the application, as thecurrent location, the last known location if the time is within thethreshold time limit.

According to the present invention there is still further provided anetwork element for providing location information in a mobilecommunication system, comprising: means for receiving a request for acurrent location of a mobile station; means for determining a time atwhich a last known location of the mobile station was determined; meansfor comparing the time to a threshold time limit; and means forproviding, as the current location, the last known location if the timeis within the threshold time limit.

The network element may further comprise means for determining a currentlocation for the mobile station if the time is not within the thresholdlimit; wherein the means for providing is adapted to provide, as thecurrent location, the obtained current location.

The means for comparing the time to the threshold time limit may beresponsive to a signal indicating the status of the mobile station.Responsive to said signal indicating that the mobile station is activethe comparing means may be disabled and a current location is determinedfor the mobile station. Responsive to said signal indicating that themobile station is idle, the comparing means may be enabled.

If a current location is not provided, the network element may beadapted to provide the last known location is provided as the currentlocation. The network element may further comprise means for storing thelast known location of a mobile station together with a time associatedwith the last known location.

The network element may further comprise means for storing the thresholdtime limit. The network element may further comprise means fordynamically adjusting the threshold time limit. The threshold time limitmay be set by a network operator. The threshold time limit may beincluded in the request for a current location.

According to a yet further aspect of the present invention there isprovided a mobile communication system including an application forproviding location dependent services and for generating a locationrequest for a user equipment; a network element for receiving therequest for a current location of a mobile station; a network elementfor determining a time at which a last known location of the mobilestation was determined and for comparing the time to a threshold timelimit; and a network element for providing, as the current location, thelast known location if the time is within the threshold time limit.

The network element for determining the time at which the last knownlocation was determined preferably includes a visitor location register.The system may implement a CAMEL framework or location services.

In embodiments, the invention thus proposes a configurable threshold foran MSC/VLR (or SGSN) which prevents unnecessary paging attempts if theMSC/VLR (or SGSN) already has sufficiently fresh location informationavailable. For the purposes of both CAMEL any time interrogation (ATI)and location services (LCS), the VLR stores the last known locationinformation for each subscriber. The threshold value is used such thatno paging is needed if the last known location information is newer thanthe threshold value, which value is set by the system operator.

Whilst the invention is particularly advantageously utilised for mobilestations in idle mode, the inventive technique may also be applied tomobile stations in active mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 illustrates an example of a CAMEL based mobile communicationsystem in which an embodiment of the invention may be implemented;

FIG. 2 is a flow diagram illustrating the steps for implementing apreferred embodiment of the invention in the communication system ofFIG. 1;

FIG. 3 illustrates the main features of a network element adapted toimplement a preferred embodiment of the present invention;

FIG. 4 illustrates a further example of a mobile communication systemimplementing location services in which an embodiment of the inventionmay be implemented; and

FIG. 5 is a flow diagram illustrating the steps for implementing apreferred embodiment of the invention in the communication system ofFIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is described herein by way of particular referenceto exemplary embodiments. The invention is not limited in itsapplicability to any particular example described herein. The inventionis particularly described in relation to a CAMEL (customisedapplications for mobile network enhanced logic) framework and a locationservices framework. However such frameworks are presented merely forease of understanding the present invention.

Referring to FIG. 1, the invention is first described with reference toa CAMEL phase 3 framework. FIG. 1 shows the main elements necessary inorder to describe the application of the present invention in a CAMELphase 3 implementation. Only such elements of the implementation areshown which are necessary for an understanding of the present invention.

Referring to FIG. 1, there is shown a core network 6 including a homelocation register (HLR) 8 and a mobile-services switching centre (MSC)10. The mobile-services switching centre 10 is associated with a visitorlocation register (VLR) 12. External to the core network 6, there isillustrated a service control point (SCP) 2. The service control point 2is associated with a GSM service control function (gsmSCF) 4. The gsmSCFin FIG. 1 is shown only by way of example, and the functional entitygsmSCF may be implemented as part of any other network element. A basestation sub system or radio access network (BSS/RAN) 14 comprises theinterface between the core network 6 and mobile stations, one of whichmobile stations is represented by mobile station (MS) 16. Although amobile station is shown in the Figures, this is for the purposes ofdescribing examples, and the mobile station may be more generallyconsidered to be user equipment.

The elements illustrated in FIG. 1 are familiar to one skilled in theart. The service control point 2 is the network element implementing thegsmSCF functionality. The gsmSCF 4 is the functional entity thatcontains the CAMEL service logic to implement operator specificservices. The present invention is particularly concerned with theprovision of location based information. Therefore the elements of FIG.1 represent those elements of the core network 6 required forimplementation of such.

The CAMEL phase 3 arrangement of FIG. 1 will now be described by way ofreference to FIGS. 2 and 3, utilising the present invention. The gsmSCF4 requests the location of the mobile station 16 by sending a MAP anytime interrogation (ATI) message to the HLR 8. This request is sent on asignal line 18 from the gsmSCF 4 to the HLR 8. The request received bythe HLR 8 identifies the mobile station 16. The HLR 8 stores theidentity of the VLR in which the mobile station 16 is currentlyregistered. The HLR 8 stores also the identity of the mobile-servicesswitching centre 10. On determining the appropriate identity, the HLR 8sends the location request to the VLR 12 via communication link 20.

The preceding actions are represented by steps 30, 32, and 34 in FIG. 2.In step 30 the application, i.e. the gsmSCF 4, requests the current MSlocation. In step 32 the HLR 8 determines the VLR 12 associated with themobile station. In step 34 the HLR request the MS location from the VLR12.

In a step 36 the visitor location register 12 and mobile-servicesswitching centre 10 determines whether the user equipment, i.e. themobile station 16, is currently active. If the mobile station 16 iscurrently active, then the location of the mobile station is known dueto the active call connection. Thus in a step 38 the mobile-servicesswitching centre returns the current cell global identity (CGI) orservice area identity (SAI) to the HLR 8 via the communication link 20.

If in step 36 it is determined that the mobile station is not active,i.e. it is in idle mode, then the MSC 10 determines the time of the lastknown location in a step 40. The VLR 12 stores the last known locationof each mobile station, together with the time at which that locationwas determined. In accordance with the present invention, in a step 42the time at which the last known location for the mobile station wasdetermined is compared to a threshold value. For example, based on thecurrent time the time elapsed since the last known location wasdetermined may be calculated, and the threshold time may be a value ofelapsed time. As is discussed further hereinbelow, the threshold time ispreferably set by the operator of the network.

The threshold time is intended to be a representation of the “freshness”of the last known location. For example, for a given application it maybe acceptable if the location information is less than a certain timeperiod old. For example certain location services may only require thatthe location information is provided within a 30 second window. In suchcases, the threshold value will be set at a 30 second time period.Further discussion in relation to the setting of the threshold value isgiven hereinbelow.

If in the step 42 it is determined that the elapsed time is less thanthe threshold time, then in step 44 the last known CGI or service areaidentity is returned to the HLR 8 on communication link 20.

If however in step 42 it is determined that the elapsed time since thelast known location was determined is greater than the threshold value,then in a step 46 the mobile station is paged through the BSS/RAN 14.The MSC 10 communicates with the BSS/RAN 14 via communication links 22.The BSS/RAN 14 sends a paging signal to the mobile station 16 on the airinterface communication link 24. Responsive to the paging signal, themobile station 16 sends a signal to the BSS/RAN 14 via the air interfacecommunication link 24, which in turn is forwarded to the mobile-servicesswitching centre 10 via the communication link 22. Following theresponse from the mobile station 16, the CGI or service area identity ofthe mobile station 16 is known, and in a step 48 the current CGI orservice area identity is returned to the HLR 8.

After return of the current CGI or service area identity in any one ofsteps 38, 44 or 48, the location information is returned to theapplication gsmSCF 4 via communication link 18 from the HLR 8.

Thus, as can be seen from the above description, the present inventionadvantageously uses a threshold value in order to determine when themobile station should be paged in order to determine its location. Thus,contrary to prior art techniques, an idle mobile station is not pagedresponsive to every location request. However, the mobile station ispaged if it is determined that the last stored location information istoo old.

The value of the threshold is determined preferably by the operator ofthe network. The threshold value may be dynamically variable, independence upon network conditions or operator requirements. Theapplication itself may also indicate to the threshold value that ittolerates. The application may send a threshold value with a locationrequest.

The value of the threshold may also vary in dependence upon an accuracyrequired. For example, if the application required to know the locationof the mobile station within an accuracy of 1 km, then a large thresholdtime may be tolerable. However if accuracy was required to be within 100m, then a small threshold value may only be tolerable. Requestedaccuracy can be indicated currently only within location servicesprocedure, not in CAMEL ATI. An example implementation of the inventionusing location services is given hereinbelow.

The threshold value may also be dynamically adjustable in dependenceupon the characteristics of the mobile station. For example if it isknow that the mobile station is fast moving, then the threshold valuemay only be a small value.

In the above described example, in the case where the mobile station iscurrently active then the threshold value is not used. However, it maybe advantageous to use the threshold value in a similar way for activelyconnected mobile stations. This is discussed further hereinbelow withreference to a different embodiment.

Referring to FIG. 3, there is illustrated elements of an exemplaryvisitor location register 12 and mobile-services switching centre 10 forimplementing a preferred embodiment of the present invention. It shouldbe noted that the elements shown in FIG. 3 are for illustrative purposesonly and do not necessarily represent elements which are essential tothe implementation of the present invention. One skilled in the art willappreciate alternative implementations of the present invention. Itshould also be noted that in FIG. 3 there is some overlap betweenfunctional elements of the mobile-services switching centre 10 and theassociated visitor location register 12.

Referring to FIG. 3, the mobile-services switching centre or visitorlocation register includes a control block 72, a difference calculatorblock 82, a comparator block 84, a current time block (or clock) 80, anda storage means 60. The storage means 60 includes the visitor locationregister reference 62 in FIG. 3, and an elapsed time special valuestorage element 70.

The control block 72 receives a location request 74 on the communicationlink 20 from the HLR 8. The control block 72 also receives a signal online 76 indicating the status of the mobile station, i.e. idle oractive. The control block 72 is provided with a communication interface78 for communicating with the various other elements of themobile-services switching centre and visitor location register 12. Thecurrent time block 80 provides a current time on line 86 to thedifference calculator 82. The visitor location register 62 receives on aline 64 an identity of a mobile station. Responsive to the identity ofthe mobile station on line 64, in conjunction with appropriate controlsignals from the control block 72 on lines 78, the time of the lastknown location of the mobile station is read out on line 68 and providesa second input to the difference calculator 82.

In this preferred embodiment, the difference calculator subtracts thetime at which the last known location was determined from the currenttime, in order to determine an elapsed time. The elapsed time is outputfrom the difference calculator on line 88, and forms a first input tothe comparator 84. A second input to the comparator 84 is provided by anelapsed time threshold value storage means 70 within the storage means60. The comparator determines whether the elapsed time on line 88 isless than or greater than the threshold value stored in the storagemeans 70. The output on line 90 of the comparator 84 therefore simplygives an indication of whether the comparison is negative or positive.

The threshold indication on line 90 is provided to the control block asone of the control signals 78.

If in the comparator 84 it is determined that the elapsed time thresholdvalue has not been exceeded, then the control block 72 controls thevisited location register 62 to read out the last known location on aline 66 which is returned to the HLR 8. If in fact the threshold valuehas been exceeded, then as described hereinabove with reference to FIGS.1 and 2 of the control block 72 initiates a paging of the mobile stationin accordance with known techniques.

A second embodiment of the present invention is now described withreference to FIGS. 4 and 5. FIG. 4 represents the network elements in amobile communication system implementing location services. Referring toFIG. 4, a core network 114 comprises a gateway mobile location centre(GMLC) 102, a home location register (HLR) 104, a mobile-servicesswitching centre (MSC) 106 including a visitor location register 108.The mobile-services switching centre 106 is associated with the radioaccess network (RAN) or base station sub system (BSS) 110, whichinterfaces with the mobile station 112. A location services (LCS) clientrepresents an application which may request the location of the mobilestation 112. The location services client 100 communicates with the GMLC102 of the core network via communication links 116. The GMLC 102communicates with the HLR 104 via communication links 118. The GMLCconnects with the MSC 106 via communication links 120. The MSC 106communicates with the RAN/BSS 110 via communication links 122. TheRAN/BSS 110 communicates with the mobile station 112 via air interfacecommunication links 124.

The operation of the location services implementation of FIG. 4 forrequesting location of the mobile station 112 in accordance with thepresent invention will be further described hereinbelow with referenceto FIG. 5.

With reference to FIG. 5, in a step 130 a client, such as LCS client100, requests a current MS location by transmitting a request oncommunication link 116 to the GMLC 102. Responsive thereto, the GMLC 102requests a current MSC address for the mobile station from the HLR 104on communication link 118, as represented by step 132. The HLR 104 thenreturns the current MSC address, in step 134, on communication link 118to the GMLC 102. The GMLC then requests the current MS location from theMSC 106, on communication link 120, as represented by step 136.

Thereafter, in a step 138, the mobile-services switching centre 106determines whether the mobile station 112 is currently active. If themobile station 112 is currently active, then in a step 140 themobile-services switching centre 106 sends a location request to theRAN/BSS 110 using existing communication link 122. Paging is notrequired, as the radio link is already established. After receiving thelocation request the RAN/BSS determines the location estimate of themobile station using conventional techniques, which may involvesignalling between the RAN/BSS 110 and the mobile station 112 over theair-interface 124.

If it is determined in step 138 that the mobile station is not active,i.e. it is in idle mode, then the mobile-services switching centre 106retrieves the last known location of the mobile station from the visitorlocation register 108. In doing so, the mobile-services switching centrealso retrieves the time of the last known location determination for themobile station 112.

This is represented by step 142 in FIG. 5.

In a step 144, the mobile-services switching centre 106 then determineswhether the time associated with the last known location is less thanthe stored threshold value. If the time is less than the storedthreshold value, then in step 150 the last known location is returned tothe GMLC 102 on communication links 120.

If in step 144 it is determined that the time of the last known locationexceeds the threshold value, then in a step 146 the mobile station ispaged. Thereafter, a location request is sent to the RAN/BSS 110. Thepaging is sent to the mobile station 112 via the RAN/BSS 110. Responsiveto the location request, the RAN/BSS determines the location estimate ofthe mobile station using conventional techniques, which may involvesignalling between the RAN/BSS 110 and the mobile station 112 over theair-interface 124. Then the RAN/BSS 110 returns the estimatedgeographical coordinate position of the mobile station to themobile-services switching centre 106 on lines 122.

Thereafter, in a step 148, the MSC 106 returns the location estimate tothe GMLC 102.

After each of steps 148 and 150, the location information is returned tothe LCS client 100 by the GMLC.

As discussed hereinabove, the use of the threshold value may also beused in relation to mobile stations which are currently active. In theembodiment of FIG. 4, such use of the threshold value may beadvantageous. If an already determined and stored location informationcan be used, then this may save radio resources in having to save afurther location request to the mobile station on the radio accessnetwork.

Thus there has been described a new technique for handling locationrequests in mobile communication systems. It is an essential part of thepresent invention that the technique is implemented responsive to alocation request. It is also an important part of the present inventionthat the threshold level is preferably dynamically changeable, and thatthe operator sets the threshold level in the mobile-services switchingcentre 106 or visitor location register 108. One possible application isthat the LCS client 100 or gsmSCF 4 provides the threshold level as partof location request data.

The invention has been described herein by way of reference to twospecific examples. However the invention is not limited to any aspectsof either of these examples. One skilled in the art will appreciate howthe invention may be modified and applied in different implementations.The scope of the invention is defined by the impended claims.

1-28. (canceled)
 29. A method of providing location information in amobile communication system, comprising the steps of: receiving arequest for a current location of a mobile station; determining a timeat which a last known location of the mobile station was determined;comparing the time to a threshold time limit; and, in response to thesaid step of comparing, providing, as the current location, the lastknown location if the time is within the threshold time limit.
 30. Amethod according to claim 29 further comprising the steps of:determining a current location of the mobile station if the time is notwithin the threshold limit; and providing, as the current location, theobtained current location.
 31. A method according to claim 29 whereinthe step of comparing the time to the threshold time limit is dependentupon the status of the mobile station.
 32. A method according to claim31 wherein if the mobile station is active the comparing step isdisabled and a current location is determined for the mobile station.33. A method according to claim 31 wherein if the status of the mobilestation is idle, the comparing step is enabled.
 34. A method accordingto claim 30, wherein if a current location is not provided, the lastknown location is provided as the current location.
 35. A methodaccording to claim 29 further comprising the step of storing the lastknown location of a mobile station together with a time associated withthe last known location.
 36. A method according to claim 29 furthercomprising the step of storing the threshold time limit.
 37. A methodaccording to claim 29 further comprising the step of dynamicallyadjusting the threshold time limit.
 38. A method according to claim 29wherein the threshold time limit is set by a network operator.
 39. Amethod according to claim 29 wherein the threshold limit is included inthe request for the current location.
 40. A method according to claim 29wherein the time is an elapsed time.
 41. A method of providing locationinformation in a mobile communication system, comprising the steps of:receiving at a network element a request from an application for acurrent location of a mobile station; determining, at the networkelement, a time at which a last known location of the mobile station wasdetermined; comparing, at the network element, the time to a thresholdtime limit; and, in response to the said step of comparing, providing tothe application, as the current location, the last known location if thetime is within the threshold time limit.
 42. A network element forproviding location information in a mobile communication system,comprising: means for receiving a request for a current location of amobile station; means for determining a time at which a last knownlocation of the mobile station was determined; means for comparing thetime to a threshold time limit; and means for providing, as the currentlocation, in response to the said step of comparing, the last knownlocation if the time is within the threshold time limit.
 43. A networkelement according to claim 42 further comprising means for determining acurrent location for the mobile station if the time is not within thethreshold limit; wherein the means for providing is adapted to provide,as the current location, the obtained current location.
 44. A networkelement according to claim 42 wherein the means for comparing the timeto the threshold time limit is responsive to a signal indicating thestatus of the mobile station.
 45. A network element according to claim44 responsive to said signal indicating that the mobile station isactive the comparing means is disabled and a current location isdetermined for the mobile station.
 46. A network element according toclaim 44 wherein responsive to said signal indicating that the mobilestation is idle, the comparing means is enabled.
 47. A network elementaccording to claim 43, wherein if a current location is not provided,the network element is adapted to provide the last known location isprovided as the current location.
 48. A network element according toclaim 42 further comprising means for storing the last known location ofa mobile station together with a time associated with the last knownlocation.
 49. A network element according to claim 42 further comprisingmeans for storing the threshold time limit.
 50. A network elementaccording to claim 42 further comprising means for dynamically adjustingthe threshold time limit.
 51. A network element according to claim 42wherein the threshold time limit is set by a network operator.
 52. Anetwork element according to claim 42 wherein the threshold time limitis included in the request for a current location.
 53. A mobilecommunication system including an application for providing locationdependent services and for generating a location request for a userequipment; a network element for receiving the request for a currentlocation of a mobile station; a network element for determining a timeat which a last known location of the mobile station was determined andfor comparing the time to a threshold time limit; and a network elementfor providing, as the current location, in response to the said step ofcomparing, the last known location if the time is within the thresholdtime limit.
 54. A mobile communication system according to claim 53,wherein the network element for determining the time at which the lastknown location was determined includes a visitor location register. 55.A mobile communication system according to claim 53 wherein the systemimplements a CAMEL framework.
 56. A mobile communication systemaccording to claim 53 wherein the system implements location services.